Flushable wrapper for absorbent pads

ABSTRACT

A FLUSHABLE WRAPPER FOR SANITARY NAPKINS, DISPOSABLE DIAPERS AND OTHER ABSORBENT PADS. THE WRAPPER COMPRISES A NON-WOVEN FIBER WEB BONDED BY A WATER-SOLUBLE ADHESIVE AND OVERPRINTED WITH ANOTHER BINDER COMPRISING A SPACED PATTERN OF WATER-INSOLUBLE ADHESIVE. THE PATTERN OF THE LATTER ADHESIVE IS ARRANGED SO AS TO PERMIT THE WEB TO BE BROKEN UP INTO PIECES APPROXIMATIG THE SIZE OF A POSTAGE STAMP WHEN THE WEB IS SOAKED IN EXCESS WATER.

NOV. 2, gg 1,F,@HAMFDMGNE` JR EI'AL 3,616,797

FLUSHABLE WRAPPER FOR ABSORBENT PADS Filed Feb. 6, 1970 NON-WOVEN WEBIMPREGNATED WITH WATER SOLUBLE BINDER- l2' INSOLUBLE BINDER le v (un wmi ma w YQ/uvm gum :mima: v f. rmm gamin n xum\ m u a Crm u mlm :mgm/ uZLom United States Patent O 3,616,797 FLUSHABLE WRAPPER FOR ABSORBENTPADS John F. Champaigne, Jr., Neenah, and Howard A. Whitehead, Appleton,Wis., assignors to Kimberly-Clark Corporation. Neenah, Wis.

Filed Feb. 6, 1970, Ser. No. 9,261 Int. Cl. A61f 13/16, 13/18 U.S. Cl.12S-290 9 Claims ABSTRACT OF THE DISCLOSURE A liushable wrapper forsanitary napkins, disposable diapers ar d other absorbent pads. Thewrapper comprises a non-woven fiber web bonded by a water-solubleadhesive and overprinted with another binder comprising a spaced patternof water-insoluble adhesive. The pattern of the latter adhesive isarranged so as to permit the web to be broken up into piecesapproximating the size of a postage stamp when the web is soaked inexcess water.

BACKGROUND OF THE INVENTION In the recently developed art directedtoward solving the problem of producingl sanitary napkins and disposablediapers which are lushable and made for disposal by deposition in thetoilet, emphasis has been placed on developing a wrapper material whichis strong enough to remain intact in the moist environment encounteredduring use, yet which will disintegrate readily when deposited in excesswater, as in modern sewerage systems. Most of the work has been pointedtowards the use of non-woven webs bonded by a binder which is basicallywater-soluble, or which can be converted from an insoluble towatersoluble stage by some simple expedient. In doing this work, it wasfound that most binders which provided a non-woven web with suicient drystrength and which met the objective of dissolving rapidly to permit theweb to disintegrate when soaked in water, did not give the websufficient wet strength to successfully survive exposure to the moistconditions encountered in actual use. As a result, critical areas ofsuch webs often failed when suspended from a conventional supportingdevice such as a sanitary belt.

It was also believed that in order for a non-woven web to be consideredcompletely ushable, it had to be capable of being broken down to itsindividual fibers after a reasonable period of soaking in theconventional sewerage disposal system. It has now been determined thatthe latter condition is not necessarily required for adequate disposal,and that if a web is devised which breaks up into small, postage stampsize pieces after soaking, the pieces easily pass through conventionaldisposal systems including septic tanks without causing problems. Thisinvention is directed to such a web.

SUMMARY OF THE INVENTION In accordance with this invention a lightweight array of initially unbonded libers in the form of a non-woven websuch as conventional carded web is lirst bonded overall with awater-soluble adhesive such as bry impregnating or spraying, or byprinting wth closely spaced, and broken or continuous, parallel lines.This web with its primary bonding of water-soluble adhesive is thenoverprinted with a pattern of a flexible water-insoluble adhesivearranged in a predetermined spacing. The pattern of the latter adhesiveis spaced with respect to the average length of the fibers in a mannerto permit the web to be broken up into small pieces or patchesapproximating the size of rice a postage stamp, i.e. up to about l" by2" in dimension, upon subjecting the bonded web to the dissolving actionof excess water.

Accordingly it is the object of the present invention to provide aflushable wrapper with improved functional strength in use, but which isstil capable of being broken up into iiushable size upon disposalthereof in a toilet.

Another object is to provide sanitary napkins and similar disposablepads with the new, improved wrapper whereby the entire product becomeslushable.

Still another object is to provide a process for fabricating an improvednon-woven web having flushable properties.

These and other objects will become apparent by reference to thefollowing specification and drawings wherein there are described variousselected embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a slightly reduced plan viewof a portion of a non-woven web made in accordance with the invention.

FIG. 2 is a similar plan view of a portion of another non-woven webembodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the preferred embodiments ofthe present inventive concept as shown in the drawings, a portion of acarded, non-woven web 12 of textile bers is illustrated in FIG. l,wherein closely spaced parallel lines of water-soluble binder 14 extendgenerally diagonally across the width of web 12. Printed over thisprimary water-soluble binder 14 is ya spaced pattern of a secondarybinder in the form of elongate segments 16 of a flexible water-insolublebinder.

The web employed in this embodiment comprised a carded web of 1.5 denier1%6" staple length rayon fibers, the said web weighing about 14 gramsper square yard. The water-soluble binder comprised a polyvinyl alco holadhesive of a type which was about 79-82% hydrolyzed, had a viscosity ofabout 22 cps. (4% water solution at 20 C.) and was readily soluble inwater. The polyvinyl alcohol was applied in an amount of about l0percent by weight based on the web weight. The parallel lines ofadhesive were spaced about 1A apart.

The water-insoluble adhesive was a plastisol resin comprising 100 partspolyvinyl chloride resin dispersed in 75 parts by weight of dioctylphthalate. The adhesive was applied in the form of a multiplicity ofparallel lines broken up into spaced segments about 1A6 wide and 11/2long with about l spaces between the segments in each line. Thesesegmented lines were disposed parallel to each other at spacings ofapproximately 11/2" between lines. The 1/2 spacing and 11/2 longsegments of adjacent lines were disposed alternately with respect toeach other providing an open arrangement resembling courses of bricks.Since the average fiber length was 1%6, a number of the fibers weretherefore long enough to span the distance between these adhesive lineswhere the brick-like segments overlapped. The amount of plastisolapplied amounted to about 0.50 gin/sq. yd. based on the weight of thebers. The plastisol was then fused and cured at a temperature of about325 F.

In the embodiment shown in FIG. 2 a 14 gram web similar to that used inthe FIG. l embodiment was bonded with a polyvinyl alcohol sprayed on tothe web in an amount to provide a uniform bonding of the libers. Thesprayed web had a solids pickup about l0 percent by weight. This bondedweb is indicated at 12. After spraying, the web was dried and thenoverprinted with a discontinuous pattern of ia fiexible water insolublebinder 116.

The polyvinyl alcohol adhesive used was the same as described for theFIG. 1 embodiment, and the water-insoluble adhesive used was the sameplastisol as described for FIG. 1, applied in about the same amount.However, the 3/16 wide segments in each of the spaced lines ofwater-insoluble adhesive were about 1/2 long and spaced 1/2 apart. Thissegment spacing in each of the parallel lines was Iarranged so that thesegments in one line were adjacent the spaces in the closest neighboringline. In this way there was no overlapping of the segment edges in oneline with the segment edges of the adjacent line, as distinguished fromthe FIG. 1 arrangement. The spaces between lines were about so that theunattached or free span of the fibers between the binder segments inevery other line was therefore about 1%". Since the average ber lengthis 1%6, the dimension between segments measured in the predominant fiberdirection (ie. vertically in the drawing), is less than the averagelength of the fibers which make up the web. In this case that dimensionis slightly more than about of the average fiber length, and a greaternumber of fibers would therefore be positively bonded on both ends thanin the FIG. 1 arrangement.

Each of these webs was used for covering sanitary napkins `and tested inuse. It was found that they displayed improved functional strength overwebs employing watersoluble binders alone and in all cases the wrapperheld up well in use. In addition, when the used napkins covered withthese wrappers were disposed of in a toilet, it was found that theWrappers broke up into small pieces after a short period of soaking andthat the entire napkins structure was dispersed by the conventionalflushing practice.

Referring again to FIGS. 1 and 2 and the accompanying description, it isnoted once more that there is apparently some critical relationship tothe spacing of the water-insoluble adhesive and the fiber length. InFIG. 1, the segments 16 in one line overlap the Segments in the nextadjacent line, so that if the average fiber length in the web is 1%6long, and the predominant direction of the fiber lay is in the verticaldirection, as viewed in the drawings, a number of the fibers aresufficiently long to span the 11/2" vertical or longitudinal distancebetween the segmented lines `and be bound on both ends. This bonding ofthe fiber ends by the spaced water-insoluble binder segments providesareas of permanent strength in the web which areas are unaffected byhigh moisture conditions. Thus, while such moisture may weaken ordissolve portions of the primary water soluble binder, the web remainsstrong by virtue of these supplementary permanent bonds. However, whenthe web is soaked in excess water and the water-soluble areas completelydissolve in a short time, the web breaks apart between these permanentlybonded segments into pieces, or patches, of postage stamp size which areeasily flushed away.

When various other webs were made in which the spacing between segmentswas varied, it was found that for dibers of 1%6 length, the dimension ofthe unbonded area between binder segments in adjacent lines, whenmeasured in the predominant fiber direction, should range from a littleless than the average fiber length, i.e. about 11/2, to aboutthree-fourths of the fiber length, i.e. close to about 1%. Under suchconditions, the web will still break up into patch size pieces in Waterwhile retaining suflicient tensile strength to be useful. Thesespacings, of course, are measured in the predominant fiber direction, asfound in the machine direction of carded webs, and which is in thevertical direction in the drawings. FIGS. 1 and 2 show two usefulembodiments within these ranges.

While a carded rayon web is described in the specific example citedabove, other fibers including both natural and synthetic may be used inthe base web. However, cellulose tlibers or lfibers of cellulosicderivation are preferred because they are biodegradable. Also, while the4 fiber lengths in the specific example are 1%6", fiber lengths in theusual staple lengths of 1/2" to about 3" are useful. The longer fibersare, of course, less desirable because they do not disperse as well.

Also, while a carded web is specified in the examples, other means offorming the web may also be employed.

In addition to the specific polyvinyl alcohol mentioned above, othercold-water soluble polyvinyl alcohols may be used. For example,polyvinyl alcohols having a percent hydrolysis in the range of about 79to about 918 are generally cold-water soluble and are suitable for thedescribed use. Viscosities of about 21 to about 28 are preferred. Thepolyvinyl alcohol may be applied by spraying, impregnating, printing orthe like. However, a printing application can be better controlled andgives better strengths for equivalent amounts. When printing is employedthe adhesives may be in the form of straight or wavy parallel lineswhich are continuous or discontinuous.

The amount of polyvinyl alcohol used can also vary in the range of about5 to l5 Ipercent by weight, but should be regulated to provide asuitable softness and drape. Excessive amounts also are inclined tobecome sticky in use, and are thus not as desirable.

While polyvinyl valcohol is preferred as the water-soluble binder, otherwater-soluble adhesives may be used, including such materials aspolyvinyl methylether, glycOl cellulose, cellulose glycolate, methylcellulose and the like.

In addition to the polyvinyl chloride adhesive mentioned in the specificexample, other flexible adhesives may be used for the water-insolublebinders. Other plastisols such as copolymers of vinyl chlorides withother vinyl resins may be used and be plasticized by organic sebacatesor adipates, as well as phthalates. Other waterinsoluble flexibleresins, both thermoplastic and thermosetting may be used including suchthings as polyolens, polyamides, cellulose acetates and acrylates, aswell as elastomeric latices including natural rubbers, butadienestyrenes, butadiene acrylonitriles and the like, and Various well knowncombinations thereof. However, for the purpose set forth herein, theseadhesives should have the necessary flexibility and softness to besuitable for direct body contact.

While the water-insoluble binder is shown and described as being appliedin straight segmented lines, a variety of shapes and sizes are feasible,an important criterion being the spacing of the binder segments withrespect to fiber lengths as set forth herein.

The structure of the absorbent pad itself is not critical as long as itis made up of the usual absorbent materials which Ibreak up yanddisintegrate easily in excess water. Among these are wood pulp fluff,cotton fibers, absorbent rayon and regenerated cellulose fibers,multiple plies of cellulose wadding and the like or combinationsthereof.

What is claimed is:

1. A flushable web, especially for use with sanitary napkins, disposablediapers `and the like, comprising a non-woven web of staple lengthfibers bonded primarily with a water-soluble adhesive and overprintedwith a water-insoluble adhesive disposed in a predetermined pattern ofspaced segments.

2.. The web of claim 1 in which said water-soluble adhesive 1simpregnated throughout said web.

3 The web of claim 1 in which said water-soluble adhesive comprises aplurality of spaced parallel lines extending substantially transverse ofthe fibers.

n 4. The web of claim 3 in which the space between said lines is lessthan the average length of said fibers.

5. The web of claim 1 wherein the unbonded span of the spaces betweensegments measured in the direction coincident with the direction of thepredominant fiber lay ranges from slightly less than the average lengthof said bers to about three-fourths of the length of said bers,

`6. The web of claim 1 wherein the water-soluble adhesive is polyvinylalcohol and the water-insoluble adhesive 1s a plastisol.

5 6 7. The web of claim 6 wherein the plastisol is polyvinyl ReferencesCited chlofide- UNITED STATES PATENTS 8. A samtary napkln comprislng anabsorbent pad en- 3 111 948 11/1963 Bur eni 128 290 closed in a wrapperof the type deined in claim 1. 3521638 .H1970 Parsh 128 290 9. A methodfor the manufacture of a ushable non- 5 woven web which comprisesbonding together an initially ROBERT F. BURNETT, Primary Examinerunbonded array of staple length fibers with a water-soluble I. 1 BELL,Assistant Examiner adhesive and overprinting said fbonded ber web with awater-insoluble adhesive applied in the form of a predeter- 10 U-S- Cl-X-`R mined pattern of spaced segments. 117--38, 45, 140 A; 128-284; ll-148, 170, 410

